In the majority of patients wihh high blood pressure, the etiology of hypertension cannot be explained on the basis of existing knowledge and it is possible that unknown humoral vasoactive factors are involved in the etiology of this disease. We, therefore, are performing studies on the systematic search, isolation, and characterization of vasoactive factors in hypertensive patients and animals. The ultimate goal of this project is to acquire new knowledge on the etiology of hypertension and to utilized it to develop better means for its prevention and therapy. Work is in progress on the isolation and characterization of a vasoactive factor(s) present in certian hypertensive patients which augments the sensitivity to angiotensin and norepinephrine. In addition, we have isolated a purified and family of renin-like vasoactive enzymes from submaxillary glands of mice. One of them has been obtaaned in crystalline form. Further studies are also being performed on the development of better techniques for isolation and purification of renins and other vasoactive factors.